The eviction of at least 60 orphans in Moldova's breakaway Trans-Dniester region has been condemned by Europe's security watchdog as "unacceptable".

Militias in the Russian-speaking region left the children homeless by closing their Moldovan boarding school.

The region requires all such schools to register as private institutions with instructions in foreign languages.

But the Organisation for Security and Co-operation in Europe demanded the immediate reopening of the school.

"Leaving children out in the street is totally unacceptable," William Hill head of the OSCE mission to Moldova, said in a statement.

And he told a news conference in Moldova's capital, Chisinau: "This crisis over schools is not needed. Such steps can destabilise the situation. The situation everywhere is very tense and rather explosive."

The orphans and children from poor families - some as young as seven-year-old - were evicted from the boarding school in Tighina, east of Chisinau, late on Monday.

Some of the older students broke through militia lines on Tuesday and barricaded themselves in the school.

The Moldovan language is virtually identical to Romanian; this was a second Moldovan-language school to be shut in Trans-Dniester in July.

Moldova was part of Romania until it was annexed by the Soviet Union in 1940. It became independent after the USSR collapsed in 1991.

The mostly Russian-speaking Trans-Dniester enclave broke away from Moldova, which has a Romanian-speaking majority, in 1990. The region is not internationally recognised.

An uneasy truce has been holding since the two fought a short war in 1992.